US 2010/0219989 corresponding to JP-4683148 discloses a ring-shaped control terminal that is worn on a finger of a user when being used. For example, when a tip of an index finger on which the control terminal is worn comes into contact with a tip of a thumb of the same hand as the index finger, a closed loop conducting path is formed. Whether or not the closed loop conducting path is formed is electrically detected, and an apparatus is controlled based on the detection result.
Specifically, the control terminal includes a pair of ring electrodes and a current sensor. The ring electrodes are arranged in parallel in a direction along the axis of the finger. The current sensor is located outside a region enclosed by the electrodes. An alternating-current (AC) signal is applied between the electrodes. When the tip of the index finger comes into contact with the tip of the thumb, an electric current flows to a measurement point at which the current sensor measures the current. In contrast, when the tip of the index finger separates from the tip of the thumb, the current does not flow to the measurement point. Thus, the control terminal can determine whether the tip of the index finger is in contact with or separated from the tip of the thumb based on the current flowing to the measuring point. Then, according to the determination result, the control terminal sends a command to an external target apparatus to control the target apparatus.
However, the control terminal disclosed in US2010/0219989 can detect only two conditions, i.e., contact or separation between the index finger and the thumb. Therefore, it is difficult for the control terminal to send various types of commands to the target apparatus.
U.S. Pat. No. 6,380,923 corresponding to JP-7-121294A discloses two another control terminals that are worn on a body of a user when being used. In the first control terminal disclosed in U.S. Pat. No. 6,380,923 a microphone sensor is worn on each of five fingers of the user to individually detect a sound that is generated when a supporting surface such as a floor is tapped with the fingers. In the second control terminal disclosed in U.S. Pat. No. 6,380,923, a microphone sensor is worn on a wrist of the user to detect which finger taps the supporting surface based on frequency characteristics caused by difference in bones of the fingers. The control terminals disclosed in U.S. Pat. No. 6,380,923 can detect three or more conditions and send various types of commands to a target apparatus based on the detected conditions.
However, in the first control terminal disclosed in U.S. Pat. No. 6,380,923 there is a need to wear the microphone sensor on each of five fingers. Therefore, it is a bother for a user to use the first control terminal. In the second control terminal disclosed in U.S. Pat. No. 6,380,923, the finger with which the supporting surface is tapped is detected based on the frequency characteristics. Since the second control terminal needs a signal processor for analyzing the frequency characteristics, it is difficult to reduce the size of the second control terminal. The present inventors consider that the sound recorded by the microphone is transmitted to the target apparatus and that the target apparatus analyzes the frequency characteristics. However, in this case, since a large amount of information is wirelessly transmitted between the second control terminal and the target apparatus, power consumption for the wireless communication is increased.